1. Field of the Invention
This invention relates to a material for liquid ejection recording, a recording head using the material, and a liquid ejection recording apparatus including the recording head.
2. Description of the Related Art
There has been known a liquid ejection recording method (an ink-jet recording method) which performs recording on a recording material (for example, paper) by discharging a recording liquid (ink) from orifices (discharge openings) provided in a recording head. It has also been known that a liquid ejection recording apparatus (an ink-jet recorder) utilizing this recording method is superior in various points, such as low noise, high-speed recording, color recording and the like.
As for a recording head used in a liquid ejection recording apparatus, there has been known a configuration consisting of at least two plates (a substrate, a top plate, and the like) joined to each other. This configuration is advantageous when multiple nozzles are formed, that is, when a plenty of discharge openings (orifices) are regularly arranged. Such kinds of recording heads have been described, for example, in U.S. Pat. No. 4,417,251 and Japanese Patent Public Disclosure (Kokai) No. 62-59672 (1987).
In Japanese Patent Public Disclosure (Kokai) No. 62-59672 (1987), there has been described a recording head, the perspective view and cross-sectional view of which are shown in FIGS. 1(a) and 1(b), respectively. The recording head is a multinozzle recording head having the configuration in which a liquid path 13 for a recording liquid is formed on a substrate 11 using a photosensitive resin film (a cured film of photosensitive resin) 12, to which a top plate 15 having a liquid reservoir 14 dug therein for storing the recording liquid is connected.
Inorganic glass is generally used for the top plate 15. The top plate 15 made of borosilicate glass has already been practically utilized.
When borosilicate glass is used for the top plate 15, there are problems in that cost for processing, such as processing of digging the above-described liquid reservoir 14, is high, it is difficult to sufficiently increase accuracy in the processing, and the like. Furthermore, there sometimes arise problems in that fine glass chips are produced from microcracks generated at the moment of the processing or the like, which penetrate into the liquid path 13 or block an inlet portion of the liquid path 13, and, as a result, the liquid path 13 is clogged, and the like.
Accordingly, it has been studied to solve the problems of the processing cost, processing accuracy, clogging of the liquid path and the like caused by inorganic glass as described above by providing the top plate 15 using resin in place of inorganic glass. However, the top plate 15 made of resin must satisfy the following properties in addition to the processing properties as described above.
First, it is required that the top plate 15 has an excellent recording-liquid-resistant property. That is, in the configuration of the head, the top plate 15 is a member constituting one surface of a wall material for the liquid path 13 and the liquid reservoir 14, and in most cases contacts the recording material when the head is operating. If the recording-liquid-resistant property of resin is inferior, there arises, for example, the problem that impurities from the resin are dissolved into the recording liquid from a portion contacting the recording liquid.
The impurities dissolved into the recording liquid include various kinds of additives (release agents, plasticizers, polymerization catalysts, flame retarders and the like) contained within the resin, and the resin itself. If such impurities are dissolved into the recording liquid, the properties of the recording liquid, such as viscosity, suface tension, pH, chromaticity and the like, sometimes change, and hence the ejection performance of the liquid from the recording head, the quality and preservative property of printed matter, and the like sometimes deteriorate. Furthermore, since a recording operation is performed by discharging a recording liquid from fine orifices (discharging openings) in a liquid ejection recording apparatus, dissolved substances within the recording liquid are deposited near discharge openings, which produce so-called clogging or a state close to clogging, causing nondischarge of the recording liquid.
For example, it has been known that, if calcium, magnesium and the like are dissolved into the recording liquid, they react with carbon dioxide near the discharge openings, and calcium carbonate and magnesium carbonate are deposited. Furthermore, in a liquid ejection recording apparatus of the type utilizing heating elements as discharge-energy generating elements, dissolved substances, such as specific polyvalent metal ions, colloidal silica and the like, are in some cases thermally decomposed on the heating elements. Decomposed deposits coat the heating elements, and remarkably weaken (hinder) the transmission of the thermal energy produced by the heating elements to the recording liquid.
As for the recording-liquid-resistant property, in addition to the above-described dissolution of the impurities, there is also the problem that the recording liquid is impregnated in a portion contacting the recording liquid of the top plate 15 made of resin to swell the portion and the smoothness of the surface is thereby lost.
The above-described problems relating to the recording-liquid-resistant property are not problems which occur only for the top plate 15, but are problems which occur when resin is used for any member having a surface contacting the recording liquid, that is, a member which functions as a wall material for the recording liquid. The members which function as wall materials for the recording liquid are, for example, an ink cartridge for housing the recording liquid, an ink tank on carriage, rigid members (a supply/recovery meter, a cap, a waste-liquid tank and the like) around the liquid path, and the like, in addition to the top plate.
Further referring to the top plate 15, it must be transparent in order to perform patterning for the photosentivitive resin film 12 by illuminating light through the top plate 15. Accordingly, resin materials having appropriate transparency, such as acrylic resin materials, diallylphthalate resin materials, diallylcarbonate resin materials, epoxy resin materials induced from epichlorohydrin, and the like are candidates for the constituent materials for the top plate 15. However, all of these resin materials sometimes cause problems in the above-described recording-liquid-resistant property.
Furthermore, since these resin materials have low glass transition temperatures, there sometimes arise problems in the heat-resistive property in working processes in that stress is produced within the resin materials due to heating during assembling and working operations of a recording head to cause peeling, warp and the like.